2,6-dichloro-4-trifluoromethyl-aniline is one of important pesticide intermediates and is used to prepare insecticidal pyrazole type compounds such as pyrazole type insecticide “Fipronil”. There are several preparation methods of 2,6-dichloro-4-trifluoromethyl-aniline and generally with these processes, 3,4-Dichlorobenzotrifluoride as starting material is subjected to ammoniation and then subjected to halogenation. However, they usually result in high production cost, great volume of generated three-wastes and difficult treatment.
U.S. Pat. No. 4,096,185 and U.S. Pat. No. 4,388,472 describe a synthesis process by which p-Chlorobenzotrifluoride reacts with liquid ammonia reaction to form 4-trifluoromethyl-aniline and the latter is then subjected to ring chlorination to form 2,6-dichloro-4-trifluoromethyl-aniline. However, the reaction for prepare 4-trifluoromethyl-aniline shall be carried out under high-temperature and high-pressure and with mixture of cuprous chloride and potassium fluoride as catalyst and its conversion ratio and final yield are very low, which makes its application and popularization very difficult.
Recently, Europe patent EP1528052A1 describe a new process of synthesis of 2,6-dichloro-4-trifluoromethyl-aniline, with which p-Chlorobenzotrifluoride as start material is at first subjected to ring chlorination to form 3,4,5-Trichlorobenzotrifluoride and 3,4-Dichlorobenzotrifluoride and then the latter is subjected to fluoridization reaction and ammoniation reaction to form 2,6-dichloro-4-trifluoromethyl aniline. Since the chlorides are liable to dissolve in water, in this process the control of water is rather strict and thus the requirements on the equipment are rather high. In addition, in this process expensive solvent N-methylpyrrolidone is used during ammoniation reaction and it is difficult to recover. Hence this process is inapplicable to industrial production.
From the above description it is clear that the existing processes for preparation of 2,6-dichloro-4-trifluoromethyl aniline have the following weaknesses: 1. high production cost due to expensive raw materials, 2. complex process and difficult industrialization, 3. low reaction conversion ratio and yield ratio, great volume of generated three-wastes and difficult treatment.